# help w/ voltage meter

1543 Views 7 Replies 7 Participants Last post by  williswires
I am trying to find out why a light isn't working (either switch or fixture) Where do I touch red prong, black prong on my voltage meter? Black wire, white, ground?? Thanks
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I am trying to find out why a light isn't working (either switch or fixture) Where do I touch red prong, black prong on my voltage meter? Black wire, white, ground?? Thanks
Touch one probe on the black and one on the white. If there is voltage, the meter will show it. The black is hot, and the white is the 'neutral.' A current should register if you touch a probe to the black and one to the ground, but that just means the circuit is properly grounded. The ground wire is NEVER supposed to carry current except when there is a short somewhere, then the current flowing through the ground trips the breaker.
Depending on what kind of meter you have, you may see
http://en.wikipedia.org/wiki/Phantom_voltage
For household power voltage measurements set the meter to at least 240 volts AC. (If you are sure you will be testing only 120 volt circuits then set the meter to at least 120 volts AC)

It does not matter which terminal or location you touch the red probe to.
thanks for the replies, however I am still confused..... touch black probe to the ??? wire, and red probe to the ??? wire. (I know black wire is hot, green/bare is ground and white is neutral)
thanks for the replies, however I am still confused..... touch black probe to the ??? wire, and red probe to the ??? wire. (I know black wire is hot, green/bare is ground and white is neutral)

Black probe to neutral or ground, red probe to hot (black or red hopefully) wire. White is usually neutral but on a switch it could be the switch leg to lite fixture.
thanks for the replies, however I am still confused..... touch black probe to the ??? wire, and red probe to the ??? wire. (I know black wire is hot, green/bare is ground and white is neutral)
It doesn't matter which probe you touch to which wire. Pick a color any color, it will work just the same. The little Neon inside your tester won't know the difference. Its just like a light bulb, it can be wired backwards and it will still work.
The critical thing to remember is that a multimeter measures voltage potential between the two probes when reading voltage. This means that it reads the voltage difference between the two probes.

You gotta remember this, because if you touch both probes to wires that happen to be both hot and on the same phase, your meter will read very little or nothing, when you actually have 120V present. Again, it reads this because it is reading the voltage difference between the two probes.

For example, if you put your meter leads on the two terminals of a light switch that has power and is turned ON, your meter will show near or at 0 volts, but you have 120V present on both terminals.
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